Fuel injection device for an internal combustion engine

ABSTRACT

A fuel injection device for an internal combustion engine includes a housing and at least one valve element which cooperates with a valve seat on an injection end of the housing. A plurality of fuel outlet conduits in the housing are associated with the valve element. In the region of the beginning of the fuel outlet conduits a flow chamber is present which is formed by at least one annular groove that is concentric with the longitudinal axis of the valve element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 03/02462 filed onJul. 23, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a fuel injection device for an internalcombustion engine, having a housing, and having at least one valveelement, which cooperates with a valve seat on an injection end of thehousing and with which at least two fuel outlet conduits in the housingare associated.

2. Description of the Prior Art

German Patent Disclosure DE 40 23 223 A1 discloses an injector with twocoaxial valve needles which are each pressed against a valve seat by ahelical compression spring. They are pressed away from the valve seatcounter to the action force of the helical compression springs when thepressure of the fuel in the region of the valve seat is increased.

The fuel outlet openings in the inner valve element are disposeddownstream of the valve seat and begin at a blind hole. The inner valveelement accordingly cooperates with a “blind-hole nozzle”. The outervalve element has its seat in the immediate vicinity of the fuel outletopening. It is known as a “sacless (vco) nozzle”.

OBJECTS AND SUMMARY OF THE INVENTION

The object of the present invention is to further develop a fuelinjection device of the type defined at the outset in such a way thatthe fuel distribution to the individual injection ports is assymmetrical as possible, and the exhaust gas behavior of the engine isimproved.

This object is attained, in a fuel injection device of the type definedat the outset, in that the fuel outlet conduits (68) associated with avalve element (36) communicate fluidically with one another through anannular groove (66).

In the fuel injection device of the invention, the advantages ofblind-hole nozzles are attainable even with fuel outlet conduitsdisposed at arbitrary points in the fuel injection device. Until now,blind-hole nozzles were limited to an embodiment with a central blindhole in the housing of the fuel injection device. However, since anannular groove can be placed at nearly any arbitrary point, markedlygreater freedom in positioning the fuel outlet conduits is now obtained.

Moreover, while on the one hand the advantages of a blind-hole nozzlecan be attained at arbitrary fuel outlet conduits in the fuel injectiondevice of the invention, at the same time the disadvantages ofblind-hole nozzles are also reduced, since the flow space can be keptcomparatively small, depending on the cross-sectional area of theannular groove.

By means of the annular groove, extremely symmetrical fuel distributionto the various fuel outlet conduits, which can be positionedarbitrarily, of a fuel injection device is made possible, and at thesame time the emissions performance of the engine is improved.

In a first refinement, it is proposed that the annular groove isembodied in the housing. Because of the relatively great wall thicknessof the housing anyway in the region of the injection end, such anannular groove does not lead to any sacrifices in terms of strength.

However, it is also possible for the annular groove to be embodied inthe valve element. It can be made there relatively simply andeconomically, because of the good accessibility.

Finally, one annular groove can be embodied in the housing and a furtherannular groove can also be embodied in the valve element. In that case,a relatively large total cross section that joins the fuel outletconduits to one another can be attained with only slight losses ofstrength at the same time.

If the annular groove has an approximately semicircular cross section,then it can be made simply. However, it can also have an asymmetricalcross section, with overall a lesser curvature upstream of the fueloutlet conduit than downstream. The result could for instance be asemi-teardrop-shaped cross section, which has advantages fluidically.

A fuel injection device that has at least two coaxial valve elements isespecially preferred, in which the annular groove is present in theregion of the fuel outlet conduits of the radially outer valve element,and the fuel outlet conduits of the radially inner valve elementoriginate at a central blind hole which is embodied on the injection endof the housing.

In this kind of fuel injection device, in principle all the fuel outletconduits accordingly have the properties of blind-hole nozzles. Only theradially inner valve element cooperates with a classical central blindbore, while conversely the radially outer valve element, because of theannular groove, has properties of a blind-hole nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention are explained in detailbelow in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view of a fuel system of an internal combustionengine, with a plurality of fuel injection devices;

FIG. 2 is a fragmentary section through one of the fuel injectiondevices of FIG. 1;

FIG. 3, a detail marked III of the fuel injection device of FIG. 2;

FIG. 4, a view similar to FIG. 3 of a modified exemplary embodiment of afuel injection device;

FIG. 5, a view similar to FIG. 3 of a further modified exemplaryembodiment of a fuel injection device; and

FIG. 6, a view similar to FIG. 3 of a further modified exemplaryembodiment of a fuel injection device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, a fuel system of an internal combustion engine is identifiedoverall by reference numeral 10. The engine itself is not shown furtherin detail.

The fuel system 10 includes a fuel tank 12, from which an electriclow-pressure fuel pump 14 pumps the fuel into a low-pressure fuel line16. This line leads to a high-pressure fuel pump 18. This pump is apiston pump, which is driven by a camshaft (not shown) of the engine. Itcompresses the fuel to a very high pressure and pumps it to a fuelcollection line 20, in which the fuel is stored at high pressure.

A plurality of fuel injection devices 22 are connected to the fuelcollection line 20. For this purpose, they have a high-pressureconnection 24. The fuel injection devices 22 inject the fuel directlyinto respective combustion chambers 26 assigned to each of them. Theoperation of the engine in general and of the fuel system 10 and inparticular the fuel injection devices 22 is controlled and regulated bya control and regulating unit 28.

The structure of one of the fuel injection devices 22 will now beexplained in detail, referring to FIGS. 2 through 4. For the sake ofsimplicity, not all the reference numerals are entered in FIG. 2.

The fuel injection device 22 includes an elongated housing 30. In thishousing, there is an elongated recess 32. In the recess, two valveelements 34 and 36 are disposed coaxially to one another. They are urgedin the direction of the lower end, in FIG. 2, of the recess 32 byrespective helical compression springs 38 and 40. The lower end of thehousing 30, in FIG. 2, is identified by reference numeral 41 and willhereinafter also be called the “injection end”, and it is shown in moredetail in FIGS. 3 and 4.

The inner valve element 34 tapers conically on its lower end, in termsof FIGS. 2 and 3. It has two regions of different conicity, betweenwhich a sealing edge 42 is formed. The region radially outward from thesealing edge 42 forms a pressure face 44, whose function will beaddressed in greater detail hereinafter. The sealing edge 42 cooperateswith a valve seat 46 in the housing.

The radially outer valve element 36 is tubular. On its outer jacketface, approximately at the level of its axial center, it has a conicalshoulder, which forms a pressure face 48 (FIG. 2). In the region of thepressure face 48, there is an annular enlargement in the recess 32 thatacts as a pressure chamber 50. This chamber communicates with thehigh-pressure connection 24 via a high-pressure conduit 52. Above thepressure chamber 50, the inside diameter of the recess 32 in the housing30 is approximately equal to the outside diameter of the outer valveelement 36. In this way, this valve element is guided in the housing 30in a fluid-tight, sliding manner. Below the pressure chamber 50, thevalve element 36 has a somewhat smaller outside diameter than the insidediameter of the recess 32. As a result, an annular flow conduit 54 isformed between the outer valve element 36 and the recess 32 and leads asfar as the injection end 41.

The outer valve element 36 is guided in a sliding seat by the innervalve element 34. Its lower end, in terms of FIGS. 2 and 3, likewisetapers conically, with two regions of different conicity. Between thesetwo regions of different conicity, there is a sealing edge 56, whichanalogously to the valve element cooperates with a valve seat 58. Theconical region radially outside the sealing edge 56 again acts as apressure face 60, whose function is explained hereinafter.

The recess 32 in the region of the injection end 41 ends in a centralblind hole 62. From it, a plurality of fuel outlet conduits 64 extendradially outward. They are distributed uniformly over the circumferenceat the injection end 41 of the housing 30.

Between the valve seat 46 of the inner valve element 34 and the valveseat 58 of the outer valve element 36, an encompassing annular groove 66that is concentric with the longitudinal axis of the recess 32 is madein the inner wall of the recess 32. It has a circular-segmental crosssection. From the encompassing annular groove 66, a plurality of fueloutlet conduits 68 extend radially outward in a straight line from endto end, that is, from the end of each fuel outlet located at the annulargroove 66 to the opposite end of each fuel outlet. They are likewisedistributed over the circumference of the injection end 41 of thehousing 30. The encompassing annular groove 66 can be seen especiallyclearly in FIG. 4, which shows the injection end 41 of the housing 30,leaving out the two valve elements 34 and 36.

The fuel injection device 22 shown in FIGS. 2 through 4 functions asfollows: At low and medium load, it suffices if comparatively littlefuel is injected by the fuel injection device 22 into the combustionchamber 26. In that case, the pressure in the fuel collection line 20 isregulated, in a manner of no further interest here, to a comparativelylow level. If an injection is to occur, then by means of a control valvenot shown in FIG. 1, the high-pressure connection 24 is made tocommunicate with the fuel collection line 20. As a result, the pressurein the pressure chamber 50 rises, and as a consequence also does so inthe annular flow conduit 54. Thus the hydraulic force acting on thepressure face 60 increases.

The fuel pressure is selected to be so high that the hydraulic forceengaging the pressure face 60 suffices to press the outer valve element36 upward, counter to the action force of the helical compression spring40, so that the sealing edge 56 lifts from the valve seat 58. As aresult, fuel can enter the encompassing annular groove 66 and fromthere, via the fuel outlet conduits 68, it can reach the combustionchamber 26 assigned to the fuel injection device 22. The pressure in thefuel collection line 20, however, is selected to be only high enoughthat the hydraulic force, engaging the pressure face 48 of the innervalve element 34 when the valve element 36 is open, does not suffice tolift the inner valve element 34 from the valve seat 46.

In an exemplary embodiment not shown, the valve element 36 maycommunicate with a control chamber, which is defined by a pressure facewhose force resultant acts in the closing direction. When the pressurein the control chamber is briefly lowered, the valve element 36, becauseof the high pressure that continues to be applied to the face 60, islifted, so that fuel can flow out.

By means of the encompassing annular groove 66, the favorable propertiesof a blind-hole nozzle are realized: In particular, the communicationamong the individual fuel outlet conduits 68 distributed over thecircumference makes the resulting injection pattern relatively uniform.

At high loads on the engine, an injection of fuel should take place onthe one hand through the fuel outlet conduits 68 and on the other,additionally, through the fuel outlet conduits 64. To that end, thepressure in the fuel collection line 20 is increased, which with thecontrol valve open is expressed by a corresponding increase in thepressure in the pressure chamber 50, in the annular flow conduit 54, andat the pressure faces 60 and 48 of the valve elements 36 and 34,respectively. The pressure now is selected to be high enough that thehydraulic force engaging the pressure face 48 of the valve element 34suffices to lift the valve element 34 from the valve seat 46, counter tothe action force of the helical compression spring 38. Through the gapthat now results between the sealing edge 42 and the valve seat 46, thefuel can flow into the central blind hole 62 and from there can emergevia the fuel outlet conduits 64 into the combustion chamber 26. At thesame time, fuel naturally also flows out into the combustion chamber 26via the encompassing annular groove 66 and the fuel outlet conduits 68.

One possible variant of a fuel injection device 22 is shown in FIG. 5.In this drawing, those regions and elements that have equivalentfunctions to regions and elements in the exemplary embodiment shown inFIGS. 2 through 4 are identified by the same reference numerals and willnot be described again here in detail.

The distinction between the fuel injection device 22 shown in FIG. 5 andthe fuel injection device 22 shown in FIGS. 2 through 4 pertains to theposition of the encompassing annular groove 66. In the embodiment shownin FIG. 5, this annular groove is not made in the inner wall of therecess 32 of the housing 30 but rather in the conical end face, locatedradially inward from the sealing edge 56, of the outer valve element 36.

A further modified embodiment of a fuel injection device 22 is shown inFIG. 6. Once again, those elements and regions which are equivalent infunction to elements and regions in FIGS. 2 through 5 have the samereference numerals and will not be explained again in detail.

In principle, the exemplary embodiment shown in FIG. 6 comprises acombination of the fuel injection device 22 of FIGS. 2 through 4 on theone hand and a fuel injection device 22 of FIG. 5 on the other: In thefuel injection device 22 shown in FIG. 6, there are in fact twoencompassing annular grooves 66 a and 66 b; one is present in the innerwall of the recess 32 of the housing 30, while the other is converselydisposed in the conical face, located radially inward of the sealingedge 56, of the outer valve element 36. In this way, an annular chamberhaving a nearly circular cross section is created, from which the fueloutlet conduits 64 extend outward.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A fuel injection device (22) for an internal combustion engine,comprising a housing (30), at least two coaxial valve elements (34, 36)which cooperate with respective valve seats (46, 58) on an injection endof the housing (30), at least two fuel outlet conduits (68) in thehousing associated with each of the valve elements (34, 36), a firstannular groove (66 a) provided in the housing (30) for providing fluidcommunication between the fuel outlet conduits associated with theradially outer valve element, the fuel outlets (68) extending from thisannular groove in a straight line from one end of each fuel outletlocated at the first annular groove (66 a) to an opposite end of eachfuel outlet, and a second annular groove (66 b) provided on the valveelement for providing fluid communication between the fuel outletconduits (68) associated with the radially outer valve element (36). 2.The fuel injection device (22) of claim 1, wherein the annular groove(66; 66 a) is embodied in the housing (30).
 3. The fuel injection device(22) of claim 2, wherein the annular groove (66) has an approximatelysemicircular cross section.
 4. The fuel injection device (22) of claim3, wherein the fuel outlet conduits (64) of the radially inner valveelement (34) begin at a central blind hole (62) which is formed on theinjection end of the housing (30).
 5. The fuel injection device (22) ofclaim 2, wherein the annular groove has an asymmetrical cross section,with a lesser total curvature upstream of the fuel outlet conduits thandownstream.
 6. The fuel injection device (22) of claim 5, wherein thefuel outlet conduits (64) of the radially inner valve element (34) beginat a central blind hole (62) which is formed on the injection end of thehousing (30).
 7. The fuel injection device (22) of claim 2, wherein thefuel outlet conduits (64) of the radially inner valve element (34) beginat a central blind hole (62) which is formed on the injection end of thehousing (30).
 8. The fuel injection device (22) of claim 1, wherein theannular groove (66; 66 b) is embodied in the valve element (36).
 9. Thefuel injection device (22) of claim 8, wherein the annular groove (66)has an approximately semicircular cross section.
 10. The fuel injectiondevice (22) of claim 8, wherein the annular groove has an asymmetricalcross section, with a lesser total curvature upstream of the fuel outletconduits than downstream.
 11. The fuel injection device (22) of claim10, wherein the fuel outlet conduits (64) of the radially inner valveelement (34) begin at a central blind hole (62) which is formed on theinjection end of the housing (30).
 12. The fuel injection device (22) ofclaim 8, wherein the fuel outlet conduits (64) of the radially innervalve element (34) begin at a central blind hole (62) which is formed onthe injection end of the housing (30).
 13. The fuel injection device(22) of claim 1, wherein the annular groove (66) comprises one annulargroove (66 a) embodied in the housing (30), and a further annular groove(66 b) embodied in the valve element (36).
 14. The fuel injection device(22) of claim 13, wherein the annular groove (66) has an approximatelysemicircular cross section.
 15. The fuel injection device (22) of claim13, wherein the fuel outlet conduits (64) of the radially inner valveelement (34) begin at a central blind hole (62) which is formed on theinjection end of the housing (30).
 16. The fuel injection device (22) ofclaim 1, wherein the annular groove (66) has an approximatelysemicircular cross section.
 17. The fuel injection device (22) of claim16, wherein the fuel outlet conduits (64) of the radially inner valveelement (34) begin at a central blind hole (62) which is formed on theinjection end of the housing (30).
 18. The fuel injection device (22) ofclaim 1, wherein the annular groove has an asymmetrical cross section,with a lesser total curvature upstream of the fuel outlet conduits thandownstream.
 19. The fuel injection device (22) of claim 18, wherein thefuel outlet conduits (64) of the radially inner valve element (34) beginat a central blind hole (62) which is formed on the injection end of thehousing (30).
 20. The fuel injection device (22) of claim 1, wherein thefuel outlet conduits (64) of the radially inner valve element (34) beginat a central blind hole (62) which is formed on the injection end of thehousing (30).